Cloud data, is it in the Cloud or on my computer
The most probable answer is Yes to both!
Which often answers the “Why is my drive full?” question.
If you installed the Cloud Software App (you don’t have to), your 150 GB of photos are on your Computer are Real-time Syncing with the Cloud storage provider. I have to check if in all ‘both’ cases the Virus Protection of the synced data is your responsibility. I believe paid cloud services have an available backup in case of catastrophes, but you should check if your Free cloud provider does backups for free plans. Like DropBox does.
There may be more than the Google Platform as one example & maybe Zoho where, if you never install their Drive App, you can store documents & photos, etc. and edit them in the cloud using a web browser.